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// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___RANGES_SINGLE_VIEW_H
#define _LIBCPP___RANGES_SINGLE_VIEW_H
#include <__concepts/constructible.h>
#include <__config>
#include <__ranges/copyable_box.h>
#include <__ranges/range_adaptor.h>
#include <__ranges/view_interface.h>
#include <__utility/forward.h>
#include <__utility/in_place.h>
#include <__utility/move.h>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER > 17
namespace ranges {
template<copy_constructible _Tp>
requires is_object_v<_Tp>
class single_view : public view_interface<single_view<_Tp>> {
__copyable_box<_Tp> __value_;
public:
_LIBCPP_HIDE_FROM_ABI
single_view() requires default_initializable<_Tp> = default;
_LIBCPP_HIDE_FROM_ABI
constexpr explicit single_view(const _Tp& __t) : __value_(in_place, __t) {}
_LIBCPP_HIDE_FROM_ABI
constexpr explicit single_view(_Tp&& __t) : __value_(in_place, std::move(__t)) {}
template<class... _Args>
requires constructible_from<_Tp, _Args...>
_LIBCPP_HIDE_FROM_ABI
constexpr explicit single_view(in_place_t, _Args&&... __args)
: __value_{in_place, std::forward<_Args>(__args)...} {}
_LIBCPP_HIDE_FROM_ABI
constexpr _Tp* begin() noexcept { return data(); }
_LIBCPP_HIDE_FROM_ABI
constexpr const _Tp* begin() const noexcept { return data(); }
_LIBCPP_HIDE_FROM_ABI
constexpr _Tp* end() noexcept { return data() + 1; }
_LIBCPP_HIDE_FROM_ABI
constexpr const _Tp* end() const noexcept { return data() + 1; }
_LIBCPP_HIDE_FROM_ABI
static constexpr size_t size() noexcept { return 1; }
_LIBCPP_HIDE_FROM_ABI
constexpr _Tp* data() noexcept { return __value_.operator->(); }
_LIBCPP_HIDE_FROM_ABI
constexpr const _Tp* data() const noexcept { return __value_.operator->(); }
};
template<class _Tp>
single_view(_Tp) -> single_view<_Tp>;
namespace views {
namespace __single_view {
struct __fn : __range_adaptor_closure<__fn> {
template<class _Range>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
constexpr auto operator()(_Range&& __range) const
noexcept(noexcept(single_view<decay_t<_Range&&>>(std::forward<_Range>(__range))))
-> decltype( single_view<decay_t<_Range&&>>(std::forward<_Range>(__range)))
{ return single_view<decay_t<_Range&&>>(std::forward<_Range>(__range)); }
};
} // namespace __single_view
inline namespace __cpo {
inline constexpr auto single = __single_view::__fn{};
} // namespace __cpo
} // namespace views
} // namespace ranges
#endif // _LIBCPP_STD_VER > 17
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___RANGES_SINGLE_VIEW_H
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